The advantages of wideband data transmission over single-mode optical fibers has become more obvious in view of the recent development of more pure silicas used for fabrication of the cores and the claddings. Of note is the observation that silica inherently possesses a relatively low attenuation of the transmitted optical energy particularly at 1.55 .mu.m. Researchers and manufacturers are eager to exploit this favorable characteristic and seek to find the proper fiber parameters to reduce the total dispersion to a minimum to eliminate the need for repeater stations and to increase the possible transmission distance of data through the fibers.
One paper has been written which stands out in view of the recent process in optical fiber fabrication that has achieved the unheard of low-loss of 0.2 db per kilometer at 1.55 .mu.m. The analysis of Dr. Ching T. Chang entitled "Minimum Dispersion in a Single-Mode Step Index Optical Fiber" and appearing in Applied Optics, 1979, 18, pages 2516 to 2522 concerned itself with the cancellation between the material and waveguide dispersions to predict the shift in the minimum dispersion wavelengths .lambda..sub.o for achieving total minimum dispersion in single-mode step-index fibers. The paper dealt extensively with various types of single-mode step-index fibers and predict minimum dispersion wavelengths to achieve zero first order dispersion accurately. By solving the LP.sub.01 mode characteristic equation, Dr. Chang could calculate accurately how much of the LP.sub.01 mode of waveguide dispersion was needed for cancellation of the material dispersion. This greater accuracy was found to result in a significant change in the minimum dispersion wavelength and second-order residual dispersion; however a further analysis seemed to be in order to provide fabricators the necessary information for making minimum loss and minimum dispersion single-mode step-index fibers.
Thus, there is a continuing need in the state-of-the-art for an improved method for fabricating single-mode, step-index fibers which take into account the relative index difference and core diameters to achieve total minimum dispersion at a 1.55 .mu.m wavelength.